DE19904765A1 - Lead-free tin-bismuth solder alloy for soldering metal parts of electronic components or equipment - Google Patents

Abstract

A lead-free tin solder alloy has a high bismuth content together with either a small amount of germanium or predetermined amounts of nickel and copper. A lead-free tin solder alloy contains 30-58% Bi and either <= 0.1% Ge or predetermined amounts of Ni and Cu. Preferred Features: The Ge-containing alloy may also contain <= 5% Ag and <= 5% Sb. The Ni- and Cu-containing alloy contains <= 0.2% Ni, <= 1% Cu and optionally <= 5% Ag, <= 5% Sb and <= 0.1% Ge.

Description

The present invention relates to solder alloys used in a solder Ver bond between metal parts of electronic components or systems can be used should. In particular, the present invention relates to lead-free (Pb-free) solder le alloys to avoid adverse effects of Pb on the environment or health.

So far, solder has been used to connect metal parts, e.g. B. an electrical Wiring in a production line for electrical components or the like. For the Soldering process should be a solder alloy excellent characteristics in terms of wettability, ductility, resistance to thermal fatigue, corrosion resistance to sion etc. There must also be the issue of pollution are noted so that the solder alloy is made without the use of Pb should be. For example, regarding the effects of Pb on health determine that Pb in any form in mammals has an accumulating internal toxicity shows. Therefore, problems of air pollution, waste Treatment in the lead smelting process and an accumulation inside the body of Babies and pregnant women due to air contact and con tamination of food and the like.

The conventional solder alloys include tin (Sn) lead (Pb) alloys, Tin (Sn) Silver (Ag) Alloys, Tin (Sn) Antimony (Sb) Alloys and Tin (Sn) bismuth (Bi) alloys. Among these, for example, contains a typical Alloy known as "63Sn-37Pb" (eutectic temperature: 183 ° C), 37% by weight of Pb, based on the total amount of its composition, and therefore it is not preferred to use this alloy practically because of the influences from Pb to the environment.

Accordingly, there is a need to create a Pb-free solder alloy with a flow temperature of about 180 ° C for the following reasons: two or multiple solder alloys with different soldering temperatures should be in two or  several soldering steps used to manufacture complex components or systems become. There is also a need to ensure the reliability of Semiconductor parts with regard to thermal cycle stability at a peak Temperature of about 125 ° C.

Any of the Pb-free alloys that are used in place of an Sn-Pb alloy has a comparatively high flow temperature. For example, the Sn-Sb alloy flow temperature of 232 to 245 ° C. In addition, the Sn-Ag alloy has one eutectic temperature of 221 ° C. A Sn7.5Bi2Ag0.5Cu solder alloy that is one of the Sn-Bi solder, has a flow temperature of 200 to 220 ° C and requires a soldering temperature of 240 to 250 ° C. Like the solder alloy Sn7,5Bi2Ag0,5Cu, is a solder alloy that contains a few percent Bi through its characterized by low ductility, in addition to the following problems: for example the first problem is their poor workability and strength. The second problem is that the solid-liquid coexistence area, in which a liquidus line and a solidus Line exist together, is broadened. Therefore, delamination, i.e. H. a Phenomenon of lifting or peeling, soldered parts that occur can be observed can result from an uneven distribution of Bi if the two parts be connected to each other.

A tin (Sn) indium (In) alloy made from an alloy preparation based on Sn with the addition of In was manufactured as a Pb-free solder alloy with a low flow temperature examined. The Sn-In alloy has a eutectic point from 118 ° C to while a bismuth (bi-) indium (in) alloy, which is further Example of a Pb-free solder alloy with a lower flow temperature has a eutectic point of 75 ° C. However, the heat is resistant The temperatures of these Pb-free alloys are too low to be practical Would find use.  

The object of the present invention is to provide a Pb-free solder alloy, which has a low flow temperature and excellent characteristic properties in terms of heat resistance and wettability and also shows one has a low melting point and good ductility.

In a first aspect of the present invention, lead-free soldering is provided medium alloy, comprising tin as the main component of an alloy preparation, in the bismuth is present in an amount of 30 to 58% by weight and germanium in one Amount of 0.1 wt .-% or less is present, based on the total amount of Alloy preparation.

In the context of this aspect of the invention, a lead-free solder Alloy further comprise at least one element selected from the group consisting of consists of silver in an amount of 5% by weight or less and antimony in one Amount of 5% by weight or less based on the total amount of the alloy accessories riding.

In a second aspect of the present invention, a lead-free is created Solder alloy, comprising tin as the main component of an alloy preparation, in which predetermined amounts of nickel and copper are added, in addition to Bismuth in an amount of 30 to 58 wt .-%, based on the total amount of Alloy preparation.

In connection with the second embodiment, the amount of nickel in the Range of 0.2% by weight or less, and the amount of copper can be in the range of 1 wt .-% or less, based on the total amount of the alloy preparation.

A lead-free solder alloy according to this embodiment can also comprise at least one element selected from the group consisting of silver  in an amount of 5% by weight or less, antimony in an amount of 5% by weight or less and germanium in an amount of 0.1% by weight or less based on the total amount of alloy preparation.

The above and other tasks, effects and features as well as advantages of present invention will become apparent from the following description of the embodiments the invention more apparent, taken together with the accompanying figures. It demonstrate:

Fig. 1 is a graph showing the dependence of the elongation (in%) of the Sn-Bi alloy coins tion according to the present invention by the addition amount of Bi (in wt .-%);

Fig. 2 is a graph showing the dependence of the tensile strength of a Sn-Bi alloy (43 wt .-% Bi) on the addition amount Ge;

Fig. 3 is a graph showing the dependence of the elongation (in%) of a Sn-Bi alloy (43% by weight Bi) on the addition amount Ge;

Figure 4 is a graphical representation of the dependence of the creep rate of the Ge content at a temperature of 100 ° C for an alloy of the tin- bismuth-type (Sn-Bi) (Bi content: 43 wt .-%). According to the present Invention;

Fig. 5 is a graphical representation of the thermal dependence of the creep speed at temperatures of 100 ° C and 120 ° C for an alloy of the tin-bismuth type (Sn-Bi) (Bi content: 43 wt .-%) according to the present Invention in addition to the characteristic properties of a tin-lead alloy (Sn-Pb).

Lead-free solder alloys according to the present invention can be obtained are made by melting the respective starting materials selected from Sn, Bi, Sb, Ag, Ge, Ni and Cu, in the necessary quantities and proportions in one electric oven. The procedures for melting the starting materials are described in State of the art, so that the description of the procedures in subsequent discussion is omitted for simplicity.

In the embodiments described below, four alloy preparations are made described in detail. Each of these preparations basically includes tin as Main component and 30 to 58 wt .-% bismuth, based on the total amount of Alloy preparation. Each of the alloys also includes the following com Components in addition to the basic components mentioned above:

In the alloy preparation according to the first embodiment, germanium is in one Amount of 0.1% by weight or less.

In the alloy preparation according to the second embodiment, silver is in one Amount of 5% by weight or less, and antimony is in an amount of 5 wt% or less, in addition to 0.1 wt% or less germanium.

In the alloy preparation according to a third embodiment, nickel and Copper included, preferably 0.2 wt% or less nickel and 1 wt% or less copper.

In an alloy preparation according to the fourth embodiment of the invention at least one element selected from the group of 5% by weight or less Silver, 5% by weight or less antimony and 0.1% by weight or less germanium, in addition to 0.2 wt% or less nickel and 1 wt% or less copper.  

Accordingly, the solder alloys according to the present invention ready as lead-free and low-temperature solder alloys which have good ductility, heat resistance and wettability, compared to conventional solder alloys.

Fig. 1 is a graphical representation of the dependence of the percentage elongation (in%) of Sn-Bi type alloys in accordance with the present invention on the Bi content (in% by weight).

In the figure, each circle indicates a measuring point of an Sn-Bi alloy, indicates each diamond indicates a measurement point of an Sn-Bi-Ag alloy, and gives each measurement point a Sn-Bi-Sb alloy. The tension rate in the elongation measurement is 0.2% / s. The ductility of the Sn-Bi alloy increases with the addition amount Bi and reaches a peak value. After this peak value is exceeded, the Ductility of the Sn-Bi alloy to the value of the eutectic preparation (Bi 58%). Of the The melting point of the eutectic preparation is 139 ° C. An elongation of 50 to 90% is observed for the Sn-Bi alloy when the Bi content is in the range of 30 to 58% by weight lies. Taking into account the fact that the percentage elongation of a Sn- Ag alloy (with 3.5% silver) is in the range of 20 to 30% and the percentage Elongation of a Sn7.5Bi2Ag0.5Cu alloy (flow temperature: about 200 ° C; this is one of the Pb-free alloys of the Sn-Bi type) is 10%, the above percent is actual elongation of the Sn-Bi alloy with a Bi content of 30 to 58% by weight sufficiently large and is the value for an Sn-Pb alloy.

The ductility of each Sn-Bi-Ag alloy and Sn-Bi-Sb alloy is lower than that of the Sn-Bi alloy when the Bi content is in the range of 30 to 58% by weight. In In this case, however, the value is still large enough to result in a perfect solder to lead bond.  

Fig. 2 is a graphical representation of the tensile strength dependence of Sn-Bi type alloys (Bi content: 43% by weight) in accordance with the present invention on the Ge content (in% by weight).

The tensile strength of the alloy is measured using a test piece with a diameter of 3 mm and a train speed of 0.2% / s at room temperature temperature. As shown in the figure, the tensile strength can be increased by adding Sb, Ag and To the Sn-Bi alloy preparation (Bi content: 43 wt .-%) can be increased. A Addition of Ge prevents oxidation of Sn. This means that 0.05 wt .-% Ge der Alloy preparation (Sn43Bi), the 43 wt .-% Bi in addition to Sn as the main com includes component, is added and this leads to an increase in tensile strength. In analogously, other alloy preparations (i.e. Sn43Bi2Ag, the 43 wt .-% Bi and 2 wt% Ag, and Sn43Bi5Sb, which contains 43 wt% Bi and 5 wt% Sb includes, each in addition to Sn as the main component) to increase the train strength of this alloy. If 0.1 wt% Ge of each of the above Alloy preparations are added, this leads to an increase in the strength of the However, alloy containing Sb lowers the strength of the alloy Ag contains, because of reaching a saturation value.

Fig. 3 is a graphical representation of the dependence of the tensile strength of the alloy prof gene of the Bi-type Sn (Bi content: 43 wt .-%) in accordance with the present invention from the Ge-content (in wt .-%).

The percentage elongation of the Sn-Bi alloy (Bi content: 43% by weight) can be determined by a Addition of Sb, Ag and Ge can be reduced. When the Ge content of 0.05% by weight 0.1% by weight is increased, the percentage elongation of the alloy containing Sb lower than that of the alloy containing Ag. In this case, the alloy however, can be used with satisfactory results, despite the facts that it shows a 30% elongation when the Ge content is 0.1% by weight.  

Next, creep deformation resistance was examined, which is a representative characteristic of the alloy in terms of thermal strength. Fig. 4 is a graphical representation of the dependence of the creep rate of the Ge content at a temperature of 100 ° C for an alloy of tin-bismuth type (Sn-Bi) (Bi content: 43 wt .-%) of the present Invention.

Although the alloy Sn43Bi, the 43 wt .-% Bi in addition to Sn as the main component contains, and the alloy Sn43Bi2Ag, the 43 wt .-% Bi and 2 wt .-% Ag additionally contains Sn as the main component, almost the same creep-deformation resistance each of them shows a decrease in creep speed (i.e. an increase creep deformation resistance) when adding Ge. The creep speed becomes smaller when the amount of Ge is increased from 0.05% by weight to 0.1% by weight, which leads to an increase in creep deformation resistance. As from the above Description is obvious, the addition of Ge has the effect of creeping Deforrna resistance to increase.

It should also be noted that the following facts have been revealed: Both the Legie tion Sn43Bi2Sb, the 43 wt .-% Bi and 2 wt .-% Sb in addition to Sn as the main com component, and the alloy Sn43Bi5Sb, the 43 wt .-% Bi and 5 wt .-% Sb in addition to Sn has a creep rate lower than that Alloy Sn43Bi2Ag comprising 43 wt% Bi and 2 wt% Ag in addition to Sn. In In this case, the addition of 0.05% by weight of Ge to these alloys has the Effect to further reduce their creep speeds. However, each of the alloys gene Sn43Bi2Sb and Sn43Bi5Sb noticeably more effective than the alloy Sn43Bi2Ag, the 43 % By weight of Bi and 2% by weight of Ag in addition to Sn. The alloy Sn43Bi2Sb0.05Ge, which comprises 43% by weight of Bi, 2% by weight of Sb and 0.05% by weight of Ge in addition to Sn, or the Alloy Sn43Bi5Sb0.1Ge, the 43 wt .-% Bi, 5 wt .-% Sb and 0.1 wt .-% Ge provides an alloy with excellent creep deformation resistance as The result is an excellent synergy between Sb and Ge in the alloy preparation tung.  

Fig. 5 is a graphical representation of the thermal dependence of the creep speed at a temperature of 100 ° C or 120 ° C for an alloy of the tin-bismuth type (Sn-Bi) (Bi content: 43 wt .-%) according to of the present invention, in addition to the corresponding data of the Sn-Pb alloy.

To estimate the thermal strength of the alloy, a creep test under Ver using a test piece with a diameter of 3 mm.

Each of the alloys having the following compositions show similar ones Trends in that thermal creep increases, i.e. H. a Alloy deforms over time under a load at elevated temperatures analogous way. These alloy compositions are: An alloy together settlement of Sn43Bi, which includes 43% by weight of Bi in addition to Sn; an alloy combination composition Sn43Bi2Sb, which includes 43 wt% Bi and 2 wt% Sb in addition to Sn; an alloy composition Sn43Bi2Sb0.05Ge, the 43 wt .-% Bi, 2 wt .-% Sb and includes 0.05% by weight of Ge in addition to Sn; and an alloy composition 63Sn37Pb, which includes 37 wt% Pb. In addition, the alloy Sn43Bi2Sb shows one stable creep deformation resistance at temperatures from 100 to 120 ° C. The Alloy Sn43Bi2Sb0.05Ge shows almost the same thermal creep effect as that Alloy 63Sn37Pb. If Sb and Ge of an alloy composition Sn30Bi added, which includes 30% by weight of Bi in addition to Sn, and an alloy composition Sn58Bi, which includes 58% by weight of Bi in addition to Sn, the same thermal creep effects are measured as in the case of the alloy Sn43Bi.

Accordingly, a tin-bismuth-type (Sn-Bi) low temperature solder alloy, which has a high creep-deformation resistance as well as a high thermal strength and ductility are obtained by using silver and germanium or Adds antimony and germanium to an Sn-Bi type alloy containing 30 to 58% by weight Bismuth along with tin is included as its main component. One can in particular  This gives a solder alloy with excellent creep-deformation resistance that antimony and germanium are added to the alloy.

The invention is further explained below with the aid of examples.

Examples

The tensile strength was measured using a test piece with a diameter of 3 mm under the condition of a tensile speed of 0.2% / s at room temperature. A test piece of the same shape was used to estimate the heat resistance, and its creep-deformation resistance under a load of 0.2 kg / mm ^{2 was} measured.

The wettability of the test piece was also determined using a meniscograph Procedure estimated.

The following table shows the results of measurements of tensile strength, elongation, Creep deformation resistance and wettability of the alloys such as those of the Sn22Bi type, the Sn43Bi type and Sn58Bi type.  

table

As shown in the table, the Sn43Bi2Ag alloy achieved by adding 2 wt% Ag to the Sn43Bi alloy is made, improvements in terms of the tensile strength, the heat resistance (creep deformation resistance) and Wettability compared to the corresponding data of the Sn43Bi alloy. A Improvement in heat resistance can be seen due to the fact that the creep speed becomes slow.

Compared to the Sn43Bi2Ag alloy, the Sn43Bi2Ag0.05Ge alloy achieves that is produced by adding 0.05% by weight of Ge to the Sn43Bi2Ag alloy, a Improvement in wettability and also excellent improvements in tensile strength resistance and heat resistance (creep deformation resistance). Despite expectations conditions according to which the heat resistance of the Sn43Bi alloy is increased by the addition of Ni the alloy would be improved due to the fact that Ni resistance against oxidation at a high melting point shows a decrease in ductility the alloy observed for the reason that Ni and Bi are an intermetallic compound can form. So it was concluded that the addition of Cu, which is a solid Solution together with Ni forms, can be effective to obtain an alloy that has improved properties of heat resistance, etc. By adding 0.1% by weight Ni and 0.5% by weight Cu to the alloy Sn43Bi gives an improved Alloy with excellent properties of tensile strength and heat resistance (Creep-deformation resistance) without impairing ductility. In this case The wettability of such an alloy drops slightly to an acceptable level Value of this property. The fact that the same effects were found was also found can be obtained by adding Cu and Ni to the Sn43Bi alloy Contains 2 wt .-% Ag, 2 wt .-% Sb or 2 wt .-% Ag and 2 wt .-% Sb.

In addition, the studies according to the invention have shown that the addition of Ge is effective for the alloy to improve the decrease in wettability. For example, a Sn43Bi2Ag alloy containing 0.05 wt% Ge shows improved Properties of tensile strength and heat resistance (creep deformation resistance  in addition to improved wettability compared to the corresponding Data of an alloy that contains no Ge. It can also have the same type of impact gene can also be obtained by adding 0.1 wt% or less Ge to one Sn43Bi alloy with Sb or with Sb and Ag. The alloy also shows Sn43Bi2Ag0.5Cu0.1Ni0.05Ge, which includes 0.05 wt% Ge, almost the same value wettability as the corresponding value of the alloy mentioned above Sn43Bi2Ag0.05Ge.

In addition, the same effects can also be obtained by adding 0.1% by weight of Ni, 0.5% by weight of Cu and 0.05% by weight of Ge to the alloy with the addition composition Sn43Bi2Sb. In the case of the Sn43Bi alloy, the 2 wt% Ag and 2 Includes wt% Sb, the addition of 0.1 wt% Ni, 0.5 wt% Cu and 0.05 Wt .-% Ge to such an alloy for good effects.

The present invention has been described in detail with reference to various Embodiments described. It is from the foregoing description for those skilled in the art in this technical field obvious changes and modifications can be carried out without departing from the invention in its broader aspects to soften. It is therefore the intention that the following claims will be all such Changes and modifications include within the scope of the invention.

Claims (5)

1. Lead-free solder alloy comprising:

• - Tin as the main component of an alloy preparation in which
• Bismuth is present in an amount of 30 to 58% by weight; and
• - Germanium is present in an amount of 0.1% by weight or less, based on the total amount of the alloy preparation.

2. A lead-free solder alloy according to claim 1, further comprising at least one element selected from the group consisting of

• Silver in an amount of 5% by weight or less; and
• - Antimony in an amount of 5% by weight or less, based on the total amount of the alloy preparation.

3. Lead-free solder alloy comprising:

• Tin as the main component of an alloy preparation, to which predetermined amounts of nickel and copper in addition to bismuth are added in an amount of 30 to 58% by weight, based on the total amount of alloy preparation.

4. A lead-free solder alloy according to claim 3, wherein

• - the amount of nickel is in the range of 0.2% by weight or less; and
• - The amount of copper is in the range of 1 wt .-% or less, based on the total amount of the alloy preparation.

5. A lead-free solder alloy according to claim 4, further comprising at least one element selected from the group consisting of

• Silver in an amount of 5% by weight or less;
• Antimony in an amount of 5% by weight or less; and
• - Germanium in an amount of 0.1% by weight or less, based on the total amount of the alloy preparation.